According to a new report from Reuters, the FBI and the Department of Homeland Security (DHS) are investigating the massive distributed denial of service attacks (DDoS) hitting the DNS provider Dyn.

That attack, which is still ongoing, has left websites as Reddit, Twitter, Spotify and others struggling to stay up. The sheer scale of the attack is due to the target: one of America’s biggest DNS hosts. Domain Name Servers, or DNS, act as a directory for the internet. DNS servers are what allow visitors who type in gizmodo.com to be routed to the correct server where that fine website is hosted. Dyn is a major player in the DNS game, so an attack on its systems was bound to cause major outages.